🇳🇬 Overview of the Lassa fever situation in Nigeria
2020-2025
Disclaimer
- References: Nigeria Centre for Disease control (NCDC), see here:
- More information: for a dynamic report of the 🇳🇬 Lassa fever situation in Nigeria , go to 🔗
The effect of seasonality on the Lassa fever incidence
- Lassa fever cases in Nigeria by week show a seasonal effect: the number of cases peaks during the dry season period (from epi week 47 - week 12).
- The seasonal increase of Lassa fever cases during the dry period may be attributed to an increase of the infected rodent population, or a seasonal behavioural change in the human population (or a mix of both) resulting in a higher risk of exposure with infected animals and/or to food or household items contaminated with rodent excreta.
Lassa fever in Nigeria: where do efforts need to focus?
Cumulatively, from January 2018 to December 2024, 75% of all Lassa fever confirmed cases were from Ondo (33%), Edo (31%) and Bauchi (11%) States.
- Total confirmed cases: 5795
- Deaths from Confirmed Cases: 1065
- Case Fatality Ratio: 20%
- Number of Health Care Workers: 227
Lassa fever confirmed cases and CFR by State, Nigeria 2020-2024
Case fatality rate (CFR) among confirmed Lassa fever cases
- From 2017-2024, CFR among all laboratory confirmed cases in Nigeria was between 16-27% and decreased over the years.
- In 2024, overall CFR for Nigeria was 16% and differed greatly by individual State.
- In general, variation of CFR is likely due to late presentation of patients and differences in case management which may indicate a need for improvement.
Lassa fever infections among healthcare workers
- From 2020-2024, a total of 212 healthcare workers (HCW) were reported among confirmed cases, that is 4% of Lassa fever cases.
- From 2020-2024, 60% of all HCW infections were from Ondo (26%), Bauchi (20%), Edo (15%) States where 75% of all Lassa fever patients were being cared for. 12% of HCW infections are reported from Ebonyi where 6% of Lassa fever patients were being cared for.
- Higher proportion of HCW in States with low incidence (10-30%).
Cumulative number of confirmed Lassa fever cases
- Nigeria has the highest burden of Lassa fever cases in West Africa.
- Strengthening of capacity for laboratory diagnostics and case management in previous years resulted in greater case detection.
- Major LF outbreaks reported in since 2018, with 5344 confirmed cases since 2020.
Seasonality of Lassa fever
- In 2025, similar trend as per previous years confirming a seasonal effect on Lassa fever incidence.
- Compared to 2024, 6% increase in the cumulative number of confirmed cases reported.
States reporting Lassa fever confirmed cases in 2025
In 2025, as of epi week 7, 89% of LF cases are from Ondo (33%), Bauchi (22%), Edo (18%), and Taraba (16%) States.
Total confirmed cases: 451
Deaths from Confirmed Cases: 89
Case Fatality Ratio: 20%
Number of Health Care Workers: 15
Lassa fever confirmed cases and CFR by State in 2025
Case fatality ratio among confirmed Lassa fever cases by State in 2025
- As of epi week 7 2025, cumulatively 451 cases and 89 deaths (CFR=20%) across 12 States have been reported
- At same period 2024, a total of 24 States reported at least one confirmed cases.
- There is a 7% decrease in the number of suspected cases reported in 2025 compared to 2024.
- In 2024, 24 States had reported at least one suspected case versus 12 in 2025 to date.
Health care worker infections 2020-2025 epiweek 7
- As of epi week 7 of 2025, there has been 15 healthcare workers infected, that is 3% of confirmed cases.
- 8 HCW infections in Ondo, 3 in Bauchi, 2 in Gombe, 1 in Edo and 1 in Taraba.
